In a timepiece mechanism, it is difficult to correctly modulate the torque ratio between two wheel sets.
This problem particularly concerns adaptation of the level of torque delivered by a barrel to an escapement mechanism by means of a going train: the value of this torque defines the oscillator amplitude, and therefore greatly affects its chronometric performance.
Likewise, the torque ratio between an oscillating weight and a barrel is one of the parameters that characterises the winding speed of a detent type escapement movement.
Generally speaking, the sizing of timepiece systems is a compromise between a high torque value when the barrel is at the maximum winding, and a low torque value when the barrel is almost let down.
There are known mechanisms allowing a constant torque to be transmitted to the going train, such as, for example, the fusee device wherein the lever arm between the chain and fusee is variable according to the state of winding of the barrel. However, such mechanisms are not devised for modification of the torque ratio via an adjustment operation.